episome Ve-po-.somN Any of a group of genetic elements consisting of DNA and capable of giving selective advantage to the bacteria in which they occur. Episomes may be attached to the bacterial cell membrane or become part of the chromosome. Cells with episomes act like males dur¬ ing conjugation, a mating process in certain bacteria. During conjugation, cells lacking the episome may receive either the episome or the episome plus the genes to which it is attached. Experiments involving gene trans-
Epicurus, bronze bust from a Greek original, c. 280-270 bc; in the Museo Archeologico Nazionale, Naples.
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epistatic gene ► Equal Rights Amendment I 627
fers from cells in which episomes have been incorporated in the chromo¬ somes have been used to determine the locations of genes on the chromosome.
epistatic gene \,e-p3-'sta-tik\ Gene that determines whether or not a trait determined by another gene will be expressed. For example, when the gene responsible for albinism occurs, the genes that determine skin color are present but not expressed; the gene for albinism is therefore called an epistatic gene.
epistemology Study of the origin, nature, and limits of human knowl¬ edge. Nearly every great philosopher has contributed to the epistemologi¬ cal literature. Some historically important issues in epistemology are: (1) whether knowledge of any kind is possible, and if so what kind; (2) whether some human knowledge is innate (i.e., present, in some sense, at birth) or whether instead all significant knowledge is acquired through experience (see empiricism; rationalism); (3) whether knowledge is inher¬ ently a mental state (see behaviourism); (4) whether certainty is a form of knowledge; and (5) whether the primary task of epistemology is to pro¬ vide justifications for broad categories of knowledge claim or merely to describe what kinds of things are known and how that knowledge is acquired. Issues related to (1) arise in the consideration of skepticism, radi¬ cal versions of which challenge the possibility of knowledge of matters of fact, knowledge of an external world, and knowledge of the existence and natures of other minds.
epistolary Vi-'pis-to-.ler-e, 1 e-pi- , stol-9-re\ novel Novel in the form of a series of letters written by one or more characters. It allows the author to present the characters’ thoughts without interference, convey events with dramatic immediacy, and present events from several points of view. It was one of the first novelistic forms to be developed. It was foreshad¬ owed by Aphra Behn’s poem cycle Love-Letters Between a Nobleman and His Sister (1683). The outstanding early example is Samuel Richardson’s Pamela (1740); distinguished later works include Tobias Smollett’s Humphry Clinker (1771) and Pierre Laclos’s Les Liaisons dangereuses (1782). The genre remained popular up to the 19th century. Its reliance on subjective points of view makes it the forerunner of the modern psy¬ chological novel.
epitaph Ve-po-.tafX Inscription in verse or prose on a tomb, or, by exten¬ sion, anything written as if to be inscribed on a tomb. Probably the ear¬ liest surviving epitaphs are those written on ancient Egyptian sarcophagi and coffins. Ancient Greek examples are often of literary interest. In Eliza¬ bethan times epitaphs began to assume a more literary character. Many of the best known are literary memorials (often deliberately witty) not intended for a tomb.
epitaxy Process of growing a crystal of a particular orientation on top of another crystal. If both crystals are of the same material, the process is known as homoepitaxy; if the materials are different, it is known as heteroepitaxy. Common types of epitaxy include vapour phase, liquid phase, and solid phase, according to the source of the atoms being arranged on the substrate. Epitaxy is most frequently employed in the production of semiconductor wafers for use in the creation of integrated circuits.
epithalamium N.e-po-tho-'la-me-onA or epithalamion X.e-po-tho- Ta-me-3n\ Nuptial song or poem in honour or praise of a bride and bride¬ groom. In ancient Greece such songs were a traditional way of invoking good fortune on a marriage and often of indulging in ribaldry. The ear¬ liest evidence for literary epithalamiums are fragments by Sappho; the oldest surviving Latin examples are three by Catullus. In the Renaissance, epithalamiums based on classical models were written in Italy, France, and England; that of Edmund Spenser (1595) is considered the finest in English.
epoch Unit of geologic time during which a rock series is deposited. It is a subdivision of a geologic period. Additional distinctions can be made by adding relative time terms, such as early, middle, and late. The use of the term is usually restricted to divisions of the Tertiary and Quaternary PERIODS.
Epona Ve-po-noX Horse goddess of the ancient Celtic religion. Associ¬ ated with kingship and fertility, she was known as Epona in Gaul, Rhi- annon in Wales, and Macha in Ireland. Her cult was found throughout the Western Roman empire and was spread by members of the Roman army, especially cavalry units.
epoxy \i-'pak-se\ Any of a class of thermosetting polymers, polyethers built up from monomers with an ether group that takes the form of a three- membered epoxide ring. The familiar two-part epoxy adhesives consist of a resin with epoxide rings at the ends of its molecules and a curing agent containing amines or anhydrides. When mixed, these react to yield, after curing, a complex network with ether groups linking the monomers. Stable, tough, and resistant to corrosive chemicals, epoxies are excellent adhesives and useful surface coatings.
EPROM \ l e-,pram\ in full erasable programmable read-only memory Form of computer memory that does not lose its content when the power supply is cut off and that can be erased and reused. EPROMs are generally employed for programs designed for repeated use (such as the BIOS) but that can be upgraded with a later version of the program.
Epstein Vep-.stlnV Sir Jacob (b. Nov. 10, 1880, New York, N.Y., U.S.—d. Aug. 21, 1959, London, Eng.) U.S.-born British sculptor. He studied in Paris and settled in England in 1905. His 18 nude figures known as the Strand Statues (1907-08) provoked charges of indecency; his nude angel on the tomb of Oscar Wilde (1912) in Paris was also attacked. In 1913 he became affiliated with Vorticism and developed a style character¬ ized by simple forms and calm surfaces carved from stone; his works often partly retained the shape of the original block, or sometimes they were modeled in plaster. He is best known for religious and allegorical figures carved in colossal blocks of stone and for bronze portrait busts of celeb¬ rities. Occasionally he produced monumental bronze groups, such as St. Michael and the Devil (1958) for Coventry Cathedral.
Epstein-Barr X.ep-.stln-'barX virus (EBV) Virus of the Herpesviridae family that is the major cause of acute infectious mononucleosis. The virus, named for two of its discoverers, infects only salivary gland cells and one type of white blood cell. Saliva is the only bodily fluid that has been proved to contain infectious EBV particles. In less-developed nations, infection with EBV occurs in almost all children before the age of 5 and is not associated with recognizable symptoms. When EBV infection is delayed until the teen or early adult years, the body commonly responds differently, resulting in mononucleosis. Other, rarer disorders have also been linked with EBV, including certain cancers. There are no specific treatments for any form of EBV infection, and no vaccines have been developed.